0xChat is a chat app. I have medium luck with this.

Amber is a key management app. I use this for signing into Amethyst and 0xChat.

Citrine is a local relay on your phone. I use this with both Primal and Amethyst.

Mutiny Wallet is a Bitcoin and Lightning wallet that lets you sign with your Nostr private key for social features.

Wavlake is a music app that allows you to listen to music, duh, but also zap and updates your Nostr status to the song you're listening to.

Fountain is a podcast and music app that allows you to follow, share, comment, and zap with Nostr.

Voyage is another Nostr social app but I haven't used it in a while.

Nostros is a other one that I haven't used in a while.

nostrapps.com for more.